Low warpage high density trench capacitor

ABSTRACT

A capacitor structure and method of forming the capacitor structure is provided, including a providing a doped region of a substrate having a two-dimensional trench array with a plurality of segments defined therein. Each of the plurality of segments has an array of a plurality of recesses extending along the substrate, where the plurality of segments are rotationally symmetric about a center of the two-dimensional trench array. A first conducting layer is presented over the surface and a bottom and sidewalls of the recesses and is insulated from the substrate by a first dielectric layer. A second conducting layer is presented over the first conducting layer and is insulated by a second dielectric layer. First and second contacts respectively connect to an exposed top surface of the first conducting layer and second conducting layer. A third contact connects to the substrate within a local region to the capacitor structure.

BACKGROUND

A trench capacitor exhibits high power density relative to some othercapacitor types within a semiconductor integrated circuit (IC). As such,trench capacitors are utilized in applications such as dynamicrandom-access memory (DRAM) storage cells, among other applications.Some examples of trench capacitors include high densitymultiple-polysilicon (multi-POLY) deep trench capacitors (DTCs) whichare utilized in advanced technology node processes.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1A illustrates a plan view of some embodiments of an integratedcircuit (IC) die comprising a trench capacitor.

FIG. 1B illustrates a partial cross-sectional view of some embodimentsthe IC die of FIG. 1A

FIG. 1C is a schematic representation of some embodiments of a trenchcapacitor under stress.

FIGS. 2A-2F illustrate a series of cross-sectional views of someembodiments of a method for forming a capacitor structure.

FIGS. 3A-3E illustrate a series of cross-sectional views of some otherembodiments of a method for forming a capacitor structure.

FIG. 4 illustrates a cross-sectional view of some embodiments of acapacitor structure.

FIGS. 5A-5C illustrate cross-sectional views of various embodiments ofelectronically coupling an IC die containing a capacitor structure toanother IC die by a wire bond, a through silicon via, or a bond pad.

FIG. 6 illustrates a plan view of some other embodiments of an IC diehaving rotationally symmetric capacitor structures.

FIG. 7 illustrates a flow chart of some embodiments of a method forforming a capacitor structure.

FIG. 8 illustrates a flow chart of some other embodiments of a methodfor forming a capacitor structure.

FIGS. 9A and 9B illustrate various views of some embodiments of a trenchcapacitor.

FIGS. 10A and 10B illustrate various views of some other embodiments ofthe trench capacitor of FIGS. 9A and 9B.

FIGS. 11A and 11B illustrate various views of some other embodiments ofthe trench capacitor of FIGS. 9A and 9B.

DETAILED DESCRIPTION

The present disclosure will now be described with reference to thedrawings wherein like reference numerals are used to refer to likeelements throughout, and wherein the illustrated structures are notnecessarily drawn to scale. It will be appreciated that this detaileddescription and the corresponding figures do not limit the scope of thepresent disclosure in any way, and that the detailed description andfigures merely provide a few examples to illustrate some ways in whichthe inventive concepts can manifest themselves.

The present disclosure provides many different embodiments, or examples,for implementing different features of this disclosure. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

It is also noted that the present disclosure presents embodiments in theform of trench capacitor structures, which may be included in anintegrated circuit (IC) such as a microprocessor, memory device, and/orsome other IC. The IC may also include various passive and activemicroelectronic devices, such as resistors, other capacitor types (e.g.,a metal-insulator-metal capacitor (MIMCAP)), inductors, diodes,metal-oxide-semiconductor field effect transistors (MOSFETs),complementary MOS (CMOS) transistors, bipolar junction transistors(BJTs), laterally diffused MOS (LDMOS) transistors, high power MOStransistors, or other types of transistors. One of ordinary skill mayrecognize other embodiments of semiconductor devices that may benefitfrom aspects of the present disclosure.

Some methods of forming a trench capacitor comprise forming atwo-dimensional array of trenches in a substrate (e.g., a wafer). Astack of conductive layers is formed covering the substrate andcompletely fill the array of trenches. Further, the conductive layersare vertically stacked and each conductive layer lines the trenches. Theconductive layers are individually patterned sequentially from a top ofthe conductive-layer stack to a bottom of the conductive-layer stack.The sequential patterning of the conductive layers forms a stack ofelectrodes respectively from the conductive layers, where the electrodesare vertically stacked and each electrode lines the trenches. Aninter-layer dielectric (ILD) layer is formed covering the substrate andthe electrode stack, and a chemical-mechanical polish (CMP) is performedinto a top of the ILD layer. Contact vias are formed extending throughthe ILD layer to the electrodes.

A challenge with the trench capacitor is that the two-dimensional trencharray has mirror symmetry in each of the two dimensions. The mirrorsymmetry leads to un-balanced stress on the substrate, which may lead towarping, breaking, or cracking of the substrate. As trench densitiesincrease (e.g., due to smaller process nodes), the foregoing issues areexpect become more prominent.

As illustrated in FIG. 1A, a plan view of some embodiments of an IC die10 is illustrated. The IC die 10 comprises a two-dimensional array 12 ofcapacitor structures 14 that are generally uniformly aligned lengthwisein a predetermined direction 15 (e.g., lengthwise in the x-direction).For ease of illustration, only some of the capacitor structures 14 arelabeled 14. As used herein, each capacitor structure 14 may comprise,for example, a trench and a plurality of layers lining the trench. Insome embodiments, each capacitor structure 14 comprises a trench, adielectric layer lining the trench, and a conductive layer lining thetrench over the dielectric layer.

FIG. 1B illustrates a cross-section of a portion 16 of the IC die 10 ofFIG. 1A, whereby an architecture of the capacitor structures 14 may beappreciated. As illustrated in FIG. 1B, the capacitor structures 14 arefully filled with conductive layers 18 (e.g., doped polysilicon) anddielectric layers 20, whereby the trench and surrounding areas form avoid-free structure 22.

It is presently appreciated that the substantially uniform alignment ofthe array 12 of capacitor structures 14 in the predetermined direction15 of FIG. 1A, for example, increases a stress 24 (illustrated as arrowsin FIGS. 1A and 1C) between the individual capacitor structures, wherebythe stresses increase a likelihood of warpage and/or fracturing of theIC die 10 as well as the wafer (not shown) on which a plurality of ICdies 10 are formed. Furthermore, as the capacitor structures 14 arefully-filled with the conductive layers 18 and dielectric layers 20 ofFIG. 1B, such filling in believed to exacerbate the lines of stress 24,as illustrated schematically in FIG. 1C.

The present disclosure thus provides various novel trench designs andlayouts for high density trench capacitors that yield less warpageassociated with the die and wafer. Accordingly, some embodiments of thepresent disclosure will be disclosed infra, wherein a novel capacitorstructure and method of forming a capacitor structure are provided.

FIGS. 2A-2F illustrate some embodiments of a capacitor structureformation, such as a double polysilicon deep trench capacitor(double-POLY DTC) formation. It is noted that while double-POLY DTC ormulti-POLY DTC formations are described herein, the present disclosuresimilarly applies to various other capacitor structures including anynumber of POLY layers. FIG. 2A, for example, illustrates a substrate100A, wherein first and second recesses 102A, 102B are formed within adoped region 104 of the substrate 100A. For DTC applications such asvolatile DRAM, a plurality of recesses are patterned in an array, whereeach recess contains an identical structure after DTC formation.

For the embodiments of FIGS. 2A-2F, the substrate 100A is a p-typesilicon substrate. Other substrate types may comprise an n-type siliconsubstrate, or another elementary semiconductor, such as germanium; acompound semiconductor including silicon carbide, gallium arsenic,gallium phosphide, indium phosphide, indium arsenide, and/or indiumantimonide; an alloy semiconductor including SiGe, GaAsP, AllnAs,AlGaAs, GalnAs, GaInP, and/or GalnAsP; or combinations thereof. In anembodiment, the substrate 100A is a semiconductor on insulator (SOI).

For the embodiments of FIGS. 2A-2F, the doped region 104 of thesubstrate 100A is formed through an ion implantation technique of ann-type dopant, in which ionized phosphors, arsenic, antimony, or someother dopant are accelerated in an electrical field and impacted on thesurface of the substrate 100A. After the dopant ions are implanted, afirst thermal anneal is performed to drive-in and to activate thedopants, in accordance with some embodiments. The first thermal annealmay, for example, utilize rapid thermal processing (RTP) anneal, spikeanneal, millisecond anneal, laser anneal, or some other annealingprocess. Spike anneals, for example, operate at peak anneal temperaturesin the order of seconds. Millisecond anneals, for example, operate atpeak anneal temperatures in the order of milliseconds. Laser anneals,for example, operate at peak anneal temperatures in the order of microseconds.

One or more etching processes, for example, may be used to form thefirst and second recesses 102A, 102B, including dry etching process(es)such as a plasma etching, wet etching process(es), or a combinationthereof. In some embodiments, the dry plasma etch comprises a bombardingthe substrate with ions (e.g., fluorocarbons, oxygen, chlorine,nitrogen, argon, helium, etc.) that dislodge portions of the materialfrom the substrate 100A. Wet etching may also be utilized to achieve anisotropic etch profile in some embodiments. For example, an etchant suchas carbon tetrafluoride (CF₄), HF, tetramethylammonium hydroxide (TMAH),combinations thereof, or the like may be used to perform the wet etchand form the first and second recesses 102A, 102B in some embodiments. Awidth 103 (e.g., in the y-direction) of the first and second recesses102A, 102B, for example, may be on the order of one micron, while alength (e.g., in the x-direction) may be approximately 5-20 times thewidth.

FIG. 2B illustrates a substrate 100B comprising the substrate 100A,wherein a first dielectric layer 106 is deposited over a bottom region107A and sidewall region 107B of the first and second recesses 102A,102B of FIG. 2A. In some embodiments, the first dielectric layer 106 ofFIG. 2B comprises oxide/nitride/oxide (ONO) composite layer. Thedeposition of the first dielectric layer may, for example, be achievedthrough chemical vapor deposition (CVD), some derivative CVD processes,or some other deposition process. Derivative CVD processes comprise lowpressure CVD (LPCVD), atomic layer CVD (ALCVD), ultrahigh vacuum CVD(UHVCVD), reduced pressure CVD (RPCVD), or any combinations thereof.

A first conducting layer 108, for example, is further deposited over thefirst dielectric layer 106, and has a substantially uniform firstthickness t₁. In some embodiments, the first conducting layer 108comprises a deposition of polysilicon (POLY). The deposition ofpolysilicon, for example, may be achieved by pyrolyzing silane (SiH₄)inside a low-pressure reactor at a temperature in a range ofapproximately 500 degrees Celsius to approximately 700 degrees Celsiusto release silicon which accumulates on the surface of the substrate100A and along the bottom and sidewall regions 107A, 107B of the firstand second recesses 102A, 102B shown in FIG. 2A.

A second dielectric layer 110 shown in FIG. 2B, for example, isdeposited over the first conducting layer 108, and a second conductinglayer 112 is deposited over the second dielectric layer 110. In someembodiments, the second dielectric layer 110 comprises an ONO compositelayer, and deposition of the second dielectric layer 110 is achievedthrough chemical vapor deposition (CVD) or some other depositionprocess.

In accordance with the present disclosure, the second conducting layer112 fills the first and second recesses 102A, 102B not filled by thefirst conducting layer 108, while advantageously maintaining an air gap113 within the first and second recesses 102A, 102B. The presentdisclosure contemplates that the air gap 113 advantageously reduces thestresses discussed above. The second conducting layer 112, for example,has a second thickness t₂ that is substantially uniform across thesurface of the substrate 100B. The width 103 of the first and secondrecesses 102A, 102B of FIG. 2A, for example, may be increased (e.g., byapproximately 0.05 microns) to accommodate the air gap 113 of FIG. 2B,in order to maintain the desired first and second thicknesses t₁, t₂ ofthe respective first and second conducting layer 108, 112. The air gap113, for example, may have a width of approximately 0.05 microns. Insome embodiments, the second conducting layer 112 may comprisepolysilicon layer (POLY). In some embodiments, the second thickness isapproximately equal to the first thickness t₁. In other embodiments, thesecond thickness t₂ is substantially greater than the first thicknesst₁.

FIG. 2C illustrates an example where a substrate 100C comprises thesubstrate 100B, and where portions of the second conducting layer 112and the second dielectric layer 110 not within the first and/or secondrecess 102A, 102B have been removed through a first planarizationprocess, such as a first CMP process. For example, the planarized firstconducting layer 108 and the planarized second conducting layer 112 havea substantially planar surface after the first CMP process is performed.In the first CMP process, for example, chemical and mechanical forcesare exerted on the substrate 100C by a rotating platen covered by apolishing pad, which in conjunction with a slurry, polishes and globallyplanarizes the substrate 100C. The slurry, for example, may includehydrogen peroxide or other suitable material.

FIG. 2D illustrates a substrate 100D comprising the substrate 100C,wherein portions of the first conducting layer 108 and the firstdielectric layer 106 have been removed by a pattern and etch process onthe surface. For example, the substrate 100D is coated with a layer ofphotoresist in a spin-on tool, aligned with a mask containing a pattern,and exposed to light which transfers the pattern into the photoresist.In some embodiments, the pattern and etch process uses a positive tonephotoresist such that exposed areas of the photoresist layer becomesoluble upon being exposed, and are subsequently removed. In someembodiments, the pattern and etch process uses a negative tonephotoresist such that exposed areas of the photoresist layer becomeinsoluble to a photoresist developer upon being exposed. The photoresistdeveloper is used to dissolve the soluble portion of the photoresist,and the exposed or unexposed features on the semiconductor substrate maythen be removed, depending upon the tone of the photoresist.

FIG. 2E illustrates a substrate 100E comprising the substrate 100D, anoxide layer 116 is disposed on a surface of the substrate 100E throughan oxidation step. An Inter-layer Dielectric (ILD) layer 118, such astetraethylorthosilicate (TEOS) or flourine or carbon-doped SiO₂, isdisposed over the oxide layer 116 by a derivative CVD processes or otherappropriate method. The ILD layer 118, for example, is configured toelectrically separate contacts formed in a subsequent patterning step,and has a dielectric constant lower than an approximate k=3.9 value ofundoped SiO₂, and as close to 1 as possible to minimize capacitivecoupling between adjacent metal and contacts.

After a planarization of the ILD layer 118 through a second CMP process,trenches are etched and filled with a conductive material (e.g., copper,tungsten, etc.) to form first second contacts 120A, 120B to the secondconducting layer 112, a third contact 120C to the first conducting layer108, and a fourth contact 120D to the doped region 104 to complete thedouble-POLY DTC structure 100F of FIG. 2F.

FIGS. 3A-3F illustrate other embodiments of a formation of a capacitorstructure. In general, while the multi-POLY DTC formation examplesillustrated and described herein comprise a specific number (e.g., two,three, etc.) of conducting and dielectric layers, any number ofconducting and dielectric layers may be used and are contemplated asfalling within the scope of the present disclosure.

The embodiments of FIG. 3A, for example, may be identical to those ofFIG. 2A, and will not be described in additional detail. FIG. 3Billustrates a substrate 200B comprising the substrate 200A, wherein afirst ONO layer 206 (e.g., a dielectric layer) is formed over the bottomregion 107A and sidewall regions 107B of the first and second recesses102A, 102B of FIG. 3A. A first POLY layer 208 (e.g., a conductive layer)of FIG. 3B having a substantially uniform thickness is further depositedover the first ONO layer 206. A second ONO layer 210 is deposited overthe first POLY layer 208, and a second POLY layer 212 of substantiallyuniform thickness is deposited over the first POLY layer. In accordancewith the present disclosure, the second POLY layer 212 further providesan air gap 214 within the first and second recesses.

FIG. 3C illustrates a substrate 200C comprising the substrate 200B,wherein portions 114 of the second POLY layer 212 and second ONO layer210 have been removed by a first pattern and etch process on thesurface, exposing a top surface of the second POLY layer 212 for contactformation.

FIG. 3D illustrates a substrate 200D comprising the substrate 200D,wherein portions of the first POLY layer 208 and first ONO layer 206have been removed by a second pattern and etch process on the surface,exposing a top surface of the doped region 104 for contact formation.

FIG. 3E illustrates a capacitor structure 200E comprising the substrate200D, wherein a poly oxide layer 116 is disposed on a surface of thesubstrate 200D, and an ILD layer 118 is disposed above the poly oxidelayer 116. After planarization of the ILD layer 118 through a CMPprocess, trenches are etched and filled with a conductive material toform first through fifth contacts 220A-220E.

In general, the present disclosure appreciates that a capacitorstructure consisting of n poly layers (or more generally, n conductivelayers) may be assembled in a similar manner as discussed above. FIG. 4,for example, illustrates some embodiments of a capacitor structure 300(e.g., a multi-POLY DTC) disposed within a doped region 104 (e.g., dopedwith phosphors, arsenic, or antimony) of a substrate 302. The capacitorstructure 300 comprises a first conducting layer 304A (e.g.,polysilicon) of a first substantially uniform thickness (t₁) disposedover a bottom region and sidewalls of a recess formed within the dopedregion 104 of the substrate 302 and over a surface of the substrate 302.The first conducting layer 304A is insulated from the substrate 302 by afirst dielectric layer 306A (e.g., oxide/nitride/oxide). A secondconducting layer 304B of a second substantially uniform thickness (t₂)is disposed over the first conducting layer 304A, and separated from thefirst conducting layer 304A by a second dielectric layer 306B. A thirdconducting layer 304C of a third substantially uniform thickness (t₃) isdisposed over the second conducting layer 304B, and separated from thesecond conducting layer 304B by a third dielectric layer 306C. This typeof structure may be repeated until an (n−1)^(th) conducting layer 304Eof an (n−1)^(th) substantially uniform thickness (t_(n−1)) is disposedover a (n−2)^(th) conducting layer 304E of an (n−2)^(th) substantiallyuniform thickness (t_(n−2)), and separated from the (n−2)^(th)conducting layer 304D by an (n−2)^(th) dielectric layer 306F.

An n^(th) conducting layer 304E is disposed over the (n−1)^(th)conducting layer 304D and insulated from the (n−1)^(th) conducting layer304D by an n^(th) dielectric layer 306F. The n^(th) conducting layer304E substantially fills a remainder of the recess not filled by thefirst through (n−1)^(th) conducting layers 304A-304D, while stillmaintaining an air gap 307, whereby the n^(th) conducting layer extendsabove the substrate 302 by an amount greater than an approximate sum ofthe first through n^(th) thicknesses.

A top surface of each of the first through n^(th) conducting layers304A-304E are exposed by multiple pattern and etch processes (i.e., n−1pattern and etch processes) over the doped region 104, such thatcontacts may be formed to the doped region 104 and the first throughn^(th) conducting layers 304A-304E. A first contact 308A (e.g., copper,tungsten, etc.) connects to the doped region 104. A second contact 308Bconnects to the exposed top surface of the first conducting layer 304A,a third contact 308C connects to the exposed top surface of the secondconducting layer 304B, a fourth contact 308D connects to the exposed topsurface of the third conducting layer 304C, an (n−1)^(th) contact 308Econnects to the exposed top surface of the (n−1)^(th) conducting layer304D, and an n^(th) contact 308E connects to the exposed top surface ofthe (n−1)^(th) conducting layer 304D.

The capacitor structures 100F, 200E, and 300 of FIGS. 2F, 3E, and 4,respectively, in general may be utilized in many IC applications. FIG.5A illustrates a first three-dimensional (3D) IC structure 400Acomprising a high-voltage (HV) or power IC 402A bonded to a capacitor IC404A comprising one of more DTC structures by an epoxy 406A, wherein theHV or power IC 402A and the capacitor IC 404A are stacked verticallyabove a substrate 408A and separated from the substrate 408A by anunderfill layer 410A. In some embodiments, the underfill layer 410A maycomprise one or more of polyimide, polyetherimide, benzocyclobutene(BCB), bismaleimide-triazine (BT), epoxy, or silicone. A plurality ofwirebond (WB) structures 412A-422A electrically couple the HV or powerIC 402A bonded to the capacitor IC 404A as well as to the substrate 408Awhich is coupled to a plurality of solder balls 424A to form the 3D ICstructure 400A.

FIG. 5B illustrates a second 3D IC structure 400B, wherein an HV orpower IC 402B and a capacitor IC 404A comprising one of more DTCstructures reside within a same package 422B, which is bonded to asubstrate 408B by an epoxy 406B. A first mini solder ball 410B couplesthe HV or power IC 402B to a first large solder ball 412B through afirst through-silicon via (TSV) 414B. Likewise, a second mini solderball 416B couples the capacitor IC 404A to a second large solder ball418B through a second TSV 420B. In some embodiments, the first largesolder ball 412B and the second large solder ball 418B, for example,comprise a flip-chip ball grid arrays (FCBGAs) for 2.5D and 3Dapplications.

FIG. 5C illustrates a third 3D IC structure 400C, wherein an HV or powerIC 402C is coupled to a capacitor IC 404C comprising one of more DTCstructures by a plurality of first and second bond pads, 406C and 410Crespectively, which reside within first and second packages, 408C and412C respectively. The HV or power IC 402C is electrically coupled to aplurality of solder balls 416C comprising a FCBGA for 2.5D and 3Dapplications through a substrate 414C.

FIG. 6 illustrates some embodiments of the present disclosure, wherebythe above-described stresses between capacitor structures may be furtherameliorated. As densities of capacitors and/or DTCs increase,manufacturing issues such as die and wafer cracking may beadvantageously reduced by providing a rotationally symmetric layout 500of a plurality of capacitors 502 on an IC die 504, as illustrated inFIG. 6. The present disclosure presently appreciates that therotationally symmetric layout 500 of the plurality of capacitors, forexample, reduces lines of stress induced by the uniform layout of thetrench capacitors described above in reference to FIG. 1A.

As illustrated in FIG. 6, the IC die 504 is illustrated in plan view,whereby a first array 506 of the capacitors 502 are generally arrangedand aligned along a first direction (e.g., along the x-direction), and asecond array 508 of the DTCs are generally arranged and aligned along asecond direction (e.g., along the y-direction). For example, the firstarray 506 and second array 508 are rotated approximately 90 degrees withrespect to one another. Accordingly, lines of stress 510 are brokenbetween the first and second arrays 506, 508, thus advantageouslydecreasing a likelihood of cracking and/or warping of the IC die 504and/or wafer (not shown) on which a plurality of dies are formed.

Numerous other layouts are also contemplated, whereby the lines ofstress 510 are broken between the first and second arrays 506, 508,whereby any number of capacitors 502 and arrays 506, 508 may beincorporated, such that the lines of stress 510 are broken between thearrays 506, 508, thus yielding less warpage and cracking of the IC die504. As such, while the rotationally symmetric layout 500 of theplurality of capacitors 502 is provided as an example, various otherlayouts, such as asymmetric layouts (not shown) are also contemplated.

Furthermore, in some embodiments, a combination of the rotationallysymmetric layout 500 of the plurality of capacitors 502 and the air gap113, 214 of FIGS. 2B and 3B is contemplated as further decreasingwarpage and cracking of the IC die 504. Accordingly, any combination ofthe air gap 113, 214 of FIGS. 2B and 3B and a layout of the plurality ofcapacitors 502 such that lines of stress 510 are broken between arrays506, 508 is contemplated as falling within the scope of the presentdisclosure.

FIG. 7 illustrates some embodiments of a method 600 of forming acapacitor structure (e.g., a double-POLY capacitor structure). While themethod 600 and subsequently method 700 of FIG. 8 are illustrated anddescribed as a series of acts or events, it will be appreciated that theillustrated ordering of such acts or events are not to be interpreted ina limiting sense. For example, some acts may occur in different ordersand/or concurrently with other acts or events apart from thoseillustrated and/or described herein. In addition, not all illustratedacts may be required to implement one or more aspects or embodiments ofthe description herein. Further, one or more of the acts depicted hereinmay be carried out in one or more separate acts and/or phases.

At act 602 a first dielectric layer is deposited over a bottom regionand sidewalls of a plurality of recesses formed within a local region ofa substrate and over a surface of the substrate. In some embodiments,the plurality of recesses define first and second arrays, wherein thefirst and second arrays are rotationally symmetric with one another(e.g., rotated 90 degrees with respect to one another). In someembodiments, the first dielectric layer comprises nitride configured toact as an insulator.

At act 604 a first conducting layer of a first thickness is depositedover the first dielectric layer. The first thickness, for example, issubstantially uniform across the surface, bottom region, and sidewallsof the substrate. In some embodiments, the first conducting layercomprises polysilicon.

At act 606 a second dielectric layer is deposited over the firstconducting layer. In some embodiments, the second dielectric layercomprises nitride configured to act as an insulator.

At act 608 a second conducting layer is deposited over the firstdielectric layer, where the second conducting layer fills a remainder ofthe recess not filled by the first conducting layer, while maintainingan air gap defined between the sidewalls of the thereof. The air gapadvantageously limits a stress associated therewith. The secondthickness, for example, is substantially uniform across the surface. Insome embodiments, the second conducting layer comprises polysilicon.

A act 610 portions of the second conducting layer and the seconddielectric layer not within the recess are removed by a CMP process, ora photolithographic etch back is utilized alternatively, or inconjunction with the CMP process.

At act 612 portions of the first conducting layer and the firstdielectric layer on the surface which are not within a local region ofthe recess are removed by a pattern and etch process.

At act 614 a first contact is formed to the first conducting layer overthe surface, a second contact is formed to the second conducting layerover the recess, and a third contact to the substrate within the localregion. In some embodiments, the local region comprises an n-type dopedregion within a vicinity of the capacitor structure.

FIG. 8 illustrates some embodiments of a method 700 of forming acapacitor structure (e.g., a multi-POLY capacitor structure).

At act 702 a plurality of first POLY layers of uniform thickness aredeposited over a bottom region and sidewalls of a recess formed within asubstrate and over a surface of the substrate. Alternatively, some otherconductive layers may be used in place of the first POLY layers. In someembodiments, the plurality of recesses define first and second arrays,wherein the first and second arrays are rotationally symmetric with oneanother (e.g., rotated 90 degrees with respect to one another). In someembodiments, the plurality of first POLY layers are separated from oneanother and the substrate by a plurality of first ONO layers.Alternatively, some other dielectric layers may be used in place of thefirst ONO layers.

At act 704 a second POLY layer is deposited over the plurality of firstPOLY layers, wherein the second POLY layer fills a remainder of therecess not filled by the plurality of first POLY layers, whilemaintaining an air gap defined between the sidewalls of the thereof.Alternatively, some other conductive layer may be used in place of thesecond POLY layer. The air gap advantageously limits a stress associatedtherewith. In some embodiments, the second POLY layer is separated fromthe first POLY layer by a second ONO layer. Alternatively, some otherdielectric layer may be used in place of the second ONO layer.

At act 706 portions of the second POLY layer and the second ONO layernot within the recess are removed with a first CMP, etch back, or acombination of the two.

At act 708 a portion of each of the plurality of first POLY layers andthe first ONO layers are removed on the surface which are not within avicinity of the recess with a plurality of first pattern and etchprocesses such that a top surface of each of the plurality of firstpolysilicon layers is exposed over the doped region.

With reference to FIGS. 9A and 9B, various views 800A, 800B of someembodiments of a trench capacitor 802 with strain relieving air gaps 804are provided. For ease of illustration, only some of the strainrelieving air gaps 804 are labeled 804. FIG. 9A is a plan view 800A ofthe trench capacitor 802. FIG. 9B is a cross-sectional view 800B of thetrench capacitor 802. The cross-sectional view 800B may, for example, betaken along line A-A′ in FIG. 9A.

As illustrated by the cross-sectional view 800A of FIG. 9A, asemiconductor substrate 806 defines a two-dimensional (2D) trench array808 of trenches 808 t. For ease of illustration, only some of thetrenches 808 t are labeled 808 t. The semiconductor substrate 806 maybe, for example, a bulk silicon substrate, a silicon-on-insulator (SOI)substrate, a group III-V substrate, or some other semiconductorsubstrate.

The 2D trench array 808 comprises a plurality of rows and a plurality ofcolumns. In some embodiments, the 2D trench array 808 comprises twocolumns (e.g., in an x dimension) and 8 rows (e.g., in a y dimension).Further, the trenches 808 t of the 2D trench array 808 have mirrorsymmetry in both dimensions of the 2D trench array 808. For example, the2D trench array 808 may be symmetric about a first axis equallybisecting the 2D trench array 808 in the x dimension, and may further besymmetric about a second axis equally bisecting the 2D trench array 808in the y dimension. In some embodiments, the trenches 808 t of the 2Dtrench array 808 have the same layout and/or the same orientation. Forexample, the trenches 808 t may each be oriented lengthwise in the xdimension. Further, in some embodiments, the trenches of each column arealigned (e.g., in the y dimension) with each other trench in the column,and/or the trenches of each row are aligned (e.g., in the x dimension)with each other trench in the row.

One or more capacitor electrodes 810 are vertically stacked (e.g., in az dimension) on the 2D trench array 808. For example, as illustrated,four capacitor electrodes may be stacked on the 2D trench array 808. Thecapacitor electrode(s) 810 partially fill the trenches 808 t and, asseen hereafter, each conformally line the trenches 808 t. Further,because the capacitor electrode(s) 810 only partially fill the trenches808 t, the capacitor electrode(s) 810 define the strain relieving airgaps 804. The strain relieving air gaps 804 each extend along the lengthof a respective one of the trenches 808 t and alleviate stress inducedin the semiconductor substrate 806 by the mirror symmetry of thetrenches 808 t. This, in turn, reduces the likelihood of thesemiconductor substrate 806 warping, breaking, or cracking. In someembodiments, widths W of the capacitor electrode(s) 810 decrease from anoutermost capacitor electrode to a centermost capacitor electrode,and/or heights H of the electrode(s) 810 decrease from the outermostcapacitor electrode to the centermost capacitor electrode.

In some embodiments, the semiconductor substrate 806 comprises a dopedwell 806 w underlying the capacitor electrode(s) 810. The doped well 806w may, for example, define another capacitor electrode, and/or may, forexample, have an opposite doping type as adjoining regions of thesemiconductor substrate 806. For example, the doped well 806 w may bep-type, whereas the adjoining regions of the semiconductor substrate 806may be n-type, or vice versa.

A plurality of contact vias 812 overlie the capacitor electrode(s) 810and, where present, the doped well 806 w. For ease of illustration, onlysome of the contact vias 812 are labeled 812. The contacts vias 812electrically couple the capacitor electrode(s) 810 and the doped well806 to an overlying (e.g., overlying in the z dimension) back end ofline (BEOL) metallization stack, where the capacitor electrode(s) 810and the doped well 806 w may be electrically coupled respectively to afirst terminal of the trench capacitor 802 and a second terminal of thetrench capacitor 802.

As illustrated by the cross-sectional view 800B of FIG. 9B, thecapacitor electrode(s) 810 each conformally line the trenches 808 t.Further, the capacitor electrode(s) 810 are each separated from thesemiconductor substrate 806 and/or an underlying capacitor electrode bya capacitor dielectric layer 814 individual to the capacitor electrode.Note that the capacitor dielectric layer(s) 814 are omitted from theplan view 800A of FIG. 9A for illustrative purposes. The capacitordielectric layer(s) 814 may be, for example, silicon nitride, siliconoxide, some other dielectric, or any combination of the foregoing.

A capping layer 816 covers the capacitor electrode(s) 810 and thecapacitor dielectric layer(s) 814, and an ILD layer 818 covers thecapping layer 816. Note that the capping layer 816 and the ILD layer 818are omitted from the plan view 800A of FIG. 9A for illustrativepurposes. The capping layer 816 and the ILD layer 818 accommodate thecontact vias 812. For ease of illustration, only some of the contactvias 812 are labeled 812. Further, the capping layer 816 may, forexample, serve as an etch stop while forming the contact vias 812. Thecapping layer 816 may be, for example, silicon nitride, silicon carbide,silicon oxide, or some other dielectric. The ILD layer 818 may be, forexample, silicon oxide, silicon nitride, a low K dielectric, some otherdielectric, or any combination of the foregoing. As used herein, a low Kdielectric is a dielectric with a dielectric constant K less than about3.9, 3, 2, or 1.

With reference to FIGS. 10A and 10B, various views 900A, 900B of someother embodiments of the trench capacitor 802 of FIGS. 9A and 9B areprovided. FIG. 10A is a plan view 900A of the trench capacitor 802. FIG.10B is a cross-sectional view 900B of the trench capacitor 802. Thecross-sectional view 900B may, for example, be representative of thetrench capacitor 802 along line A in FIG. 10A, line B in FIG. 10A, lineC in FIG. 10A, line D in FIG. 10A, each of lines A-D in FIG. 10A, or anycombination of the foregoing.

As illustrated, instead of the strain relieving air gaps 804, rotationalsymmetry in the 2D trench array 808 alleviate stress induced in thesemiconductor substrate 806 by the trenches 808 t. The 2D trench array808 is divided into four segments 808 s, and the segments 808 s are eachrotated about 90 degrees relative to an adjoining segment as one rotatesabout a center CNTR of the 2D trench array 808. The segments 808 s havethe same number of trenches 808 t and, in some embodiments, the sameshape and/or the same size. Further, the segments 808 s each border anouter edge of the 2D trench array 808. In some embodiments, the trenches808 t have the same layout across the segments 808 s. Further, in someembodiments, the trenches of each segment have the same layout and/orthe same orientation as each other trench in the segment.

With reference to FIGS. 11A and 11B, various views 1000A, 1000B of someother embodiments of the trench capacitor 802 of FIGS. 9A and 9B areprovided. FIG. 11A is a plan view 1000A of the trench capacitor 802.FIG. 11B is a cross-sectional view 1000B of the trench capacitor 802.The cross-sectional view 1000B may, for example, be representative ofthe trench capacitor 802 along line A in FIG. 11A, line B in FIG. 11A,line C in FIG. 11A, line D in FIG. 11A, each of lines A-D in FIG. 11A,or any combination of the foregoing. As illustrated, the strainrelieving air gaps 804 of FIGS. 9A and 9B and the rotational symmetry ofFIGS. 10A and 10B alleviate stress induced in the semiconductorsubstrate 806 by the trenches 808 t.

Therefore, it will be appreciated that some embodiments of the presentdisclosure relate to a capacitor structure and a method of forming acapacitor structure.

In some embodiments, a method of forming a capacitor structure isdisclosed. The method comprises forming a two-dimensional trench arraywithin a substrate, wherein the two-dimensional trench array has aplurality of segments defined therein. The plurality of segments, forexample, are rotationally symmetric about a center of thetwo-dimensional trench array. Each of the plurality of segmentscomprises an array of a plurality of recesses having a predeterminedlength extending along a surface of the substrate. A first dielectriclayer is deposited over a bottom region and sidewalls of the pluralityof recesses and over the surface of the substrate. A first conductinglayer of a first thickness is deposited over the first dielectric layer,wherein the first thickness is substantially uniform. A seconddielectric layer is deposited over the first conducting layer, and asecond conducting layer of a second thickness is deposited over thesecond dielectric layer, wherein the second thickness is substantiallyuniform. Portions of the second conducting layer and the seconddielectric layer not within the recess are removed, and portions of thefirst conducting layer and the first dielectric layer on the surfacewhich are not within a local region of the plurality of recesses areremoved. A first contact to the first conducting layer is formed overthe surface, a second contact to the second conducting layer is formed,and a third contact to the substrate is formed within a doped region ofthe substrate.

In some embodiments, the method comprises depositing the secondconductive layer such that the second conductive layer fills a remainderof the recess not filled by the first conductive layer while maintainingan air gap between the respective sidewalls of the plurality ofrecesses.

In some embodiments, a capacitor structure is disclosed. The capacitorstructure comprises a doped region of a substrate having atwo-dimensional trench array defined therein. The two-dimensional arrayhas a plurality of segments defined therein, wherein each of theplurality of segments comprises an array of a plurality of recesses inthe substrate having a predetermined length extending along a surface ofthe substrate. The plurality of segments are rotationally symmetricabout a center of the two-dimensional trench array. A first conductinglayer of a first thickness is disposed over a bottom region andsidewalls of the plurality of recesses and over the surface of thesubstrate. The first conducting layer, for example, is insulated fromthe substrate by a first dielectric layer. A second conducting layer isdisposed over the first conducting layer and is insulated from the firstconducting layer by a second dielectric layer. A first contact isconnected to an exposed top surface the first conducting layer, a secondcontact connected to the second conducting layer, and a third contactconnected to the substrate within a local region to the capacitorstructure.

In some embodiments, a semiconductor die is provided. The semiconductordie comprises a plurality of capacitor structures defined in asubstrate. Each of the plurality of capacitor structures comprises atwo-dimensional trench array having a plurality of segments definedtherein. The plurality of segments are rotationally symmetric about acenter of the two-dimensional trench array, wherein each of theplurality of segments comprises an array of a plurality of recesseshaving a predetermined length extending along a surface of thesubstrate. A first conducting layer of a first thickness is disposedover a bottom region and sidewalls of the plurality of recesses and overthe surface of the substrate, wherein the first conducting layer isinsulated from the substrate by a first dielectric layer. A secondconducting layer is further disposed over the first conducting layer andis insulated from the first conducting layer by a second dielectriclayer.

Although the disclosure has been shown and described with respect to acertain aspect or various aspects, equivalent alterations andmodifications will occur to others of ordinary skill in the art uponreading and understanding this specification and the annexed drawings.In particular regard to the various functions performed by the abovedescribed components (assemblies, devices, circuits, etc.), the terms(including a reference to a “means”) used to describe such componentsare intended to correspond, unless otherwise indicated, to any componentwhich performs the specified function of the described component (i.e.,that is functionally equivalent), even though not structurallyequivalent to the disclosed structure which performs the function in theherein illustrated exemplary embodiments of the disclosure. In addition,while a particular feature of the disclosure may have been disclosedwith respect to only one of several aspects of the disclosure, suchfeature may be combined with one or more other features of the otheraspects as may be desired and advantageous for any given or particularapplication. Furthermore, to the extent that the terms “including”,“includes”, “having”, “has”, “with”, or variants thereof are used ineither the detailed description and the claims, such terms are intendedto be inclusive in a manner similar to the term “comprising”.

1-11. (canceled)
 12. A semiconductor die, comprising: a plurality ofcapacitor structures defined in a substrate, wherein each of theplurality of capacitor structures comprises: a two-dimensional trencharray having a plurality of segments defined therein, wherein theplurality of segments are rotationally symmetric about a center of thetwo-dimensional trench array, and wherein each of the plurality ofsegments comprises an array of a plurality of recesses having apredetermined length extending along a surface of the substrate; a firstdielectric layer contacting a bottom region and sidewalls of theplurality of recesses and the surface of the substrate; a firstconducting layer of a first thickness disposed over the bottom regionand sidewalls of the plurality of recesses and over the surface of thesubstrate, wherein the first conducting layer is insulated from thesubstrate by the first dielectric layer; and a second conducting layerdisposed over the first conducting layer and insulated from the firstconducting layer by a second dielectric layer.
 13. The semiconductor dieof claim 12, wherein the plurality of segments comprise a first arrayextending in first direction and a second array extending in a seconddirection, wherein the first direction is generally perpendicular to thesecond direction.
 14. The semiconductor die of claim 13, wherein eachcapacitor structure comprises two first arrays and two second arrays,wherein each of the first arrays are diametrically opposed to oneanother about the center of the respective capacitor structure, andwherein each of the second arrays are diametrically opposed to oneanother about the center of the respective capacitor structure, whereinthe two first arrays and two second arrays define a rotationallysymmetric layout.
 15. The semiconductor die of claim 12, wherein thesecond conducting layer fills a remainder of the plurality of recessesnot filled by the first conducting layer while maintaining an air gapbetween the sidewalls of the respective plurality of recesses.
 16. Thesemiconductor die of claim 12, further comprising: a first contactconnected to the first conducting layer over the surface of thesubstrate; a second contact connected to the second conducting layer;and a third contact connected to the substrate within a local region tothe plurality of capacitor structures.
 17. The semiconductor die ofclaim 16, wherein the substrate comprises a p-type silicon substrate,and wherein the local region comprises an n-type doped region within avicinity of the plurality of capacitor structures.
 18. The semiconductordie of claim 12, wherein the first and second conducting layers comprisepolysilicon.
 19. The semiconductor die of claim 12, wherein the firstand second dielectric layers comprise oxide/nitride/oxide.
 20. Thesemiconductor die of claim 12, wherein the plurality of capacitorstructures are electronically coupled to an integrated circuit by a wirebond, a through silicon via, or a bond pad.
 21. The semiconductor die ofclaim 12, wherein the plurality of capacitor structures reside within adynamic random-access memory storage cell.
 22. A semiconductor die,comprising: a plurality of capacitor structures defined in a substrate,wherein each of the plurality of capacitor structures comprises: atwo-dimensional trench array having a plurality of segments definedtherein, wherein the plurality of segments are rotationally symmetricabout a center of the two-dimensional trench array, and wherein each ofthe plurality of segments comprises an array of a plurality of recesseshaving a predetermined length extending along a surface of thesubstrate; a first dielectric layer contacting a bottom region andsidewalls of the plurality of recesses and the surface of the substrate;a first conducting layer of a first thickness disposed over the bottomregion and sidewalls of the plurality of recesses and over the surfaceof the substrate, wherein the first conducting layer is insulated fromthe substrate by the first dielectric layer; and a second conductinglayer disposed over the first conducting layer and insulated from thefirst conducting layer by a second dielectric layer, wherein the secondconducting layer fills a remainder of the plurality of recesses notfilled by the first conducting layer while maintaining an air gapbetween the sidewalls of the respective plurality of recesses.
 23. Thesemiconductor die of claim 22, wherein the plurality of segmentscomprise a first array extending in first direction and a second arrayextending in a second direction, wherein the first direction isgenerally perpendicular to the second direction.
 24. The semiconductordie of claim 23, wherein each of the plurality of capacitor structurescomprises two first arrays and two second arrays, wherein each of thefirst arrays are diametrically opposed to one another about the centerof the respective capacitor structure, and wherein each of the secondarrays are diametrically opposed to one another about the center of therespective capacitor structure, wherein the two first arrays and twosecond arrays define a rotationally symmetric layout.
 25. Thesemiconductor die of claim 22, further comprising: a first contactconnected to the first conducting layer over the surface of thesubstrate; a second contact connected to the second conducting layer;and a third contact connected to the substrate within a local region tothe plurality of capacitor structures.
 26. The semiconductor die ofclaim 25, wherein the substrate comprises a p-type silicon substrate,and wherein the local region comprises an n-type doped region within avicinity of the plurality of capacitor structures.
 27. The semiconductordie of claim 22, wherein the first and second conducting layers comprisepolysilicon.
 28. The semiconductor die of claim 22, wherein the firstand second dielectric layers comprise oxide/nitride/oxide.
 29. Thesemiconductor die of claim 22, wherein the plurality of capacitorstructures are electronically coupled to an integrated circuit by a wirebond, a through silicon via, or a bond pad.
 30. The semiconductor die ofclaim 22, further comprising a dynamic random-access memory storagecell, wherein the plurality of capacitor structures reside within thedynamic random-access memory storage cell.
 31. A semiconductor die,comprising: a plurality of capacitor structures defined within asubstrate, wherein each of the plurality of capacitor structurescomprises: a doped region of the substrate having a two-dimensionaltrench array defined therein, the two-dimensional array having aplurality of segments defined therein, wherein each of the plurality ofsegments comprises an array of a plurality of recesses in the substratehaving a predetermined length extending along a surface of thesubstrate, and wherein the plurality of segments are rotationallysymmetric about a center of the two-dimensional trench array; a firstdielectric layer contacting a bottom region and sidewalls of theplurality of recesses and the surface of the substrate; a firstconducting layer of a first thickness disposed over the bottom regionand sidewalls of the plurality of recesses and over the surface of thesubstrate, wherein the first conducting layer is insulated from thesubstrate by the first dielectric layer; a second dielectric layer; anda second conducting layer disposed over the first conducting layer andinsulated from the first conducting layer by the second dielectriclayer.